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October 2023: WRS MS student Jeremy Laurich defends thesis on factors influencing wild rice nutrition. Congrats, Jeremy!
October 2023: Johnson group co-hosts wild rice research roundtable at which dozens of state, tribal, and university researchers and natural resources management staff attend and share research about wild rice. Check out the agenda here!
Jan 2023: WRS MS student Anna Peterson joins Johnson group to study the effect of Lake Association governance and organizational practices on water quality. In collaboration with Afton Clarke-Sather from Geography, funded by U of MN Institute on the Environment. Welcome, Anna!
September 2022: Nate and colleague Chan Lan Chun present at regional AWWA a conferences about biologically-driven sulfate removal wastewater. The small pilot system continues to remove sulfate and hydrogen sulfide from industrial wastewater at a regional power facility
July 2022: Kelsey Hogan defends thesis on wastewater particle control helping to meet stringent permit limits in Great Lakes region. Congrats, Kelsey!
April 2022: Alum Sophie LaFond-Hudson has paper published in JGR Biogeosciences describing how sulfur impacts wild rice life cycles: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022JG006809
February 2022: New UMD Chemical Engineering alum Nick Eshleman joins Johnson lab to support the sulfate wastewater treatment project. Welcome, Nick!
January 2022: New WRS graduate student Jeremy Laurich joings group to work on research related to how the growth environment of wild rice impacts the nutritional quality. Funded through the U of MN's Healthy Foods Healthy Lives initiative. Welcome, Jeremy!
November 2021: Johnson and colleagues contribute to: "On the Water Trail series" with a description of how mercury enters and biomagnifies in the St Louis River Estuary food web: https://www.youtube.com/playlist?list=PLSqxcFoS8NZwjGQ9Cub3Gjkq94itu1AJX
November 2021: Amanda Brennan successfully defends her PhD dissertation in Water Resources Science. Her creativity, persistence, and smarts continue to amaze me. Congratulations, Dr. Brennan!
June 2021: Geordee Spilkia successfully defends her MS thesis in Water Resources Science. She is headed for Portland to begin a new adventure with Integral Consulting. Congrats, Geordee and nice work!
March 2021: Amanda Brennan's second PhD paper published in ES&T. We introduce the BR (bioavailability ratio) and show how variance in contaminant partitioning can be characterized with a stochastic model and used to translate among contaminant activity in various phases relevant to sediment assessments & management.
November 2020: Paper with Dan Jones (now of NMT) published in ES&T related to microbes that methylate mercury and interactions with a large, distinct, controlled sulfide gradient. We suggest that, when the potential for sulfide inhibition of mercury methylation is accounted for, a diverse hgc+ community methylates mercury faster than a homogeneous community.
June 2020: Kelsey Hogan arrived in Duluth to begin her MS studies in Civil Engineering. She is working this summer on some related work due to COVID-induced staffing re-shuffles, but will begin work on the wastewater Hg project in the fall.
March 2020: Sophie's paper on the impact of sulfate on life stage progression of wild rice is in press in Aquatic Botony.
Conclusion: wild rice grown in conditions of elevated sulfate delay seed production, limiting the time available to take up nitrogen to fill seeds.
September 2019: Logan Becker & Mitch Jans joined the group in September/August to help get the habitat restoration mercury project off the ground. They've been working hard!
We are hoping to fill these buckets with mud from the St Louis River and watch in detail how mercury transformations and bioaccumulation occur under different potential restoration practices.
August 2019: Geordee Spilkia joined our lab to work on the wastewater mercury project. From PA via NOLA, she's enjoued the 6 weeks of Duluth summer... and is now looking for a good pair of boots...
July 2019: Two new projects starting this summer!
The first, with MN legislature funding with MPCA as a partner will seek to understand the factors controlling the efficiency of wastewater treatment plants in removing mercury. Plants in the Great Lakes basin are asked to remove mercury down to 1.8 nanograms per liter, that's 1.8 parts per trillion! Standards this low are needed because mercury is so strongly bioaccumulative. In some lakes & rivers with water having 1.8 ng/kg mercury, fish can have more than 1,000,000 ng, well above the State of MN's recommendation of less that 200,000 for unlimited consumption.
The second project, with EPA Great Lakes Restoration Initiative funding in collaboration with MPCA, is also related to mercury. When shallow water habitat is restored in the St Louis River Estuary, ecological improvements in terms of plant, invertebrate, fish, and wildlife populations are expected. However, the extent to which these wholesale ecological changes may impact mercury bioaccumulation are not known. We are making measurements in the estuary, in outdoor mesocosms, and in laboratory experiments to understand how these ecological restoration practices will impact mercury bioaccumulation.
June 2019: Afton Douville, a CE undergraduate, joined the group to help us develop an understanding of how mercury behaves in MN wastewater treatment plants.
May 2019: A paper with John Pastor and Ed Swain hit the press in Environmental Toxicology and Chemistry. The accumulation of sulfur in the context of sediment iron is used to explain impacts to wild rice populations in long-term, self-perpetuating mesocosms. This work is companion to several other papers: Myrbo et al. 2017a (mesocosms), Myrbo et al. 2017b (field), Pollman et al. 2017 (structural equation modeling), Pastor et al. 2017 (hydroponics and mesocosms) that described the science underlying the Minnesota Pollution Control Agency's efforts to understand the impacts of sulfur on wild rice.
Feb 2019: A paper with Dan Jones (Minnesota misses you!) describing molecular evidence for novel microbes involved in mercury methylation in sulfate-impacted lakes downstream from mining region of the St Louis River Watershed is in press at ISME. The findings suggest that the methylating community is more diverse in a heavily sulfur-impacted water column and sediment and that sulfate-rich freshwaters that contain complex organic substrates to support diverse geochemical niches are good places to look for and study the diversity of mercury methylators.
Nov 2018: Group alumni Myrna Girald-Perez presented a poster based on NSF-REU research related to the influence of the Lake Superior seiche in driving oxidation processes in coarse-grained soils. The results suggest that, in response to cyclical wetting and drying cycles, the extent to which redox-active reaction byproducts are retained in sediment porewater is related both the proximity to the soil-water interface and the inundation frequency.
Oct 2018: Sophie's paper describing the accumulation of FeS on wild rice roots and decreased nitrogen uptake in seeds was published in Biogeochemistry. The conceptual model presented suggests a tight coupling between the plant life cycle and redox processes in the very near rooting zone and that these processes are distinct from and perhaps decoupled from those occurring in the bulk sediment and porewater.
Jul 2018: Amber White defended her thesis and headed for a the Environmental Chemistry and Technology PhD program at UW Madison to study photodegradation of trace pharmaceuticals. We will miss you Amber!
Jul 2018: Marissa Castro joins the group as a MS student in the WRS program. Her research will continue Amber's work on mercury entry points to the food web in the St Louis River Estuary.
Apr 2018: Amber white wins the prestigious NSF Graduate Research Fellowship. Nice work, Amber, we're proud of you!
Mar 2018: Nate presented Sophie's research at the National ACS meeting in New Orleans, LA. He met lots of old friends from Austin and got to meet new ones at a session on "Redox & Interfacial Dynamics Among Coupled Biogeochemical Cycles of Fe, S, Minerals & Organic Matter: Implications to Multiscale Behaviors of Contaminants, Carbon & Nutrients." He even got to see one last lecture from Dr. Lawler!
Jan 2018: Amanda's paper on the use of SPME to evaluate contamination at habitat restoration sites was published in IEAM. Results showed that compared to direct measures of PAHs in sediment porewater, toxicity was overpredicted by the use of standard partitioning assumptions. Additionally, bioaccumulation was more consistent with SPME-quantified porewater concentrations than 1 carbon or 2 carbon partitioning estimates.
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